Search Results (55)

To investigate the influence of dry connection methods on the seismic behavior of assembled composite walls, four assembled composite walls were designed and tested. Various dry connection techniques were adopted for the horizontal interfaces, namely sleeve grouting connection, welding connection, box connection, and bolted connection. The failure process, failure mode, bearing capacity, rigidity, steel bar strain, and energy absorption performance of the specimens were investigated through quasi-static cyclic loading tests. The results indicate that all types of connectors can effectively transfer loads and satisfy the conceptual design principle of “strong joint and weak component”. The damage evolution of the specimens is essentially identical, and the limiting drift angles all exceed 1/90. In addition, the shear resistance of the specimens with different connection methods is preliminarily analyzed and estimated. Full article

Grouted sleeve connectors are critical components in precast concrete structural joints. This study investigates the effects of grouting defect location, quantity, and grout strength on the bond–slip constitutive relationship at the steel–grout interface in fully grouted sleeves. Fifteen centrally loaded pull-out specimens were designed using the controlled variable method and tested under monotonic tension. Failure modes, ultimate load, bond stress, and slip characteristics were analyzed. Numerical modeling was performed using ABAQUS, and a mathematical bond–slip constitutive model was developed. The experimental results show that all specimens with a single defect failed by tensile fracture of the reinforcing bar, whereas those with multiple defects exhibited bar pull-out failure, which most significantly degraded connection performance. Grout strength positively correlated with interfacial bond performance. Deviation of the water-to-binder ratio from the standard value reduced grout strength, leading to decreases in bond strength, ultimate load, and slip. The apparent increase in bond stress under multiple defects was attributed to the reduced effective anchorage area rather than enhanced interfacial bonding, resulting in the lowest actual ultimate load among all scenarios. The established bond–slip constitutive model achieved a coefficient of determination R² ≥ 0.96, indicating excellent fit. The finite element simulations agreed well with test data and accurately reproduced the bond–slip response under various defect conditions. The proposed constitutive model and finite element modeling approach provide a theoretical and quantitative basis for performance assessment of grouted sleeve connectors in engineering practice. Full article

The construction of single-story industrial halls in high-seismicity regions requires reliable beam-to-column connections to ensure adequate structural stiffness and strength. This paper investigates the emulative performance of a rigid precast beam–column connection utilizing threaded couplers and grouted corrugated steel sleeves. An experimental pro-gram was conducted on five scaled specimens—one monolithic reference and four pre-cast—subjected to quasi-static cyclic loading. The objective was to verify if the precast system achieved emulative behavior. Experimental results confirm this goal was fully achieved: the precast specimen exhibited a maximum recorded force nearly identical to the value recorded for the monolithic reference. Furthermore, the total dissipated energy for the precast joint had only a marginal 2.6% difference from the monolithic reference. Results demonstrate that the proposed solution provides emulative behavior consistent with monolithic casting. Specifically, the specimens achieved plastic deformation capacities exceeding 3%, surpassing current seismic design code requirements. While smaller diameter rebars (D14) experienced tensile failure at approximately 3% to 4% drift due to strain localization, specimen with larger D25 bars reached 4% drift without major damage. This paper concludes that the connection is suitable for seismic applications provided large diameter rebars (≥20 mm) are used. Full article

This study aims to enhance the damage controllability and overall seismic resilience of assembled underground structures under earthquake actions. To achieve this, three types of prefabricated roof–sidewall composite joints are proposed based on the design concepts of cogging for force transfer and local strengthening. These include the high-strength bolt–cogging–grouting sleeve joint (HCG), the prestressed steel strand–cogging–grouting sleeve joint (PCG), and the UHPC–cogging–grouting sleeve joint (UCG). Following the principle of positioning joints in regions of low structural stress, four 1/4-scale reinforced concrete (RC) specimens were designed and fabricated, including one cast-in-place (CIP) reference specimen and three precast RC specimens. Quasi-static tests were carried out to systematically evaluate the seismic behavior and internal force distribution of each specimen. Numerical validation was also performed using ABAQUS. The results show that both UHPC and a reasonable application of prestressing can effectively inhibit crack initiation and damage propagation at the joint seams. When the composite joints are positioned outside the plastic hinge region, they provide a reliable load transfer path for the reinforcement. The HCG and UCG joints significantly enhance the load-bearing capacity and energy dissipation capacity of the specimens. Their ductility and energy dissipation both achieve a seismic performance equivalent to that of the CIP specimen. Furthermore, damage in these specimens is predominantly confined to the designated plastic hinge region of the roof. This effectively mitigates shear damage in the roof–sidewall connection zone (RSC). Although the PCG joint improves the initial stiffness of the specimen, its energy dissipation capacity and ductility are reduced. It also causes damage to be transferred to the RSC. This leads to increased shear deformation and premature shear failure in this zone. Consequently, both UHPC and a reasonable application of prestressing can be used for the prefabrication of underground structures. Positioning the joints outside the roof plastic hinge zone can effectively achieve the seismic design goal of “strong joint, weak component”. Full article

With the vigorous promotion of the modernization of China’s construction industry, the proportion of prefabricated buildings in new construction projects has increased steadily. Grouted sleeve connection is a mainstream joining method for prefabricated components, and the performance of grouting materials is crucial to connection reliability. In this study, a modified polyurethane composite (MPC) was developed as a novel sleeve grouting material, and seven grouted splice specimens with different steel bar strength grades and anchorage lengths were fabricated for uniaxial tensile tests. The mechanical properties of MPC and the connection performance of specimens were systematically investigated, and the effects of steel bar strength grade and anchorage length on ultimate load, average bond strength, and strain characteristics were quantitatively analyzed. The results show that MPC has excellent fluidity, and its mechanical strengths meet the specified requirements. Increasing steel bar strength grade and anchorage length significantly improves ultimate load: at a 6d anchorage length, the ultimate load of the S600 series (HRB600E) is 44.85% higher than that of the S400 series (HRB400E); extending the S400 series’ anchorage length from 4d to 8d increases ultimate load by 50.61%. Average bond strength decreases with increasing anchorage length (S400-MPC-8d is 24.70% lower than S400-MPC-4d) but increases with higher steel bar strength grade (S600-MPC-6d is 32.37% higher than S400-MPC-6d). The sleeve remains elastic during the test, ensuring safety. Prediction formulas for average bond strength under slip failure were established, with good agreement between predicted and experimental results. For both HRB400E and HTRB600E steel bars, considering safety and installation errors, a critical anchorage length of 8d is recommended for engineering design. Full article

Precast bridge columns offer efficiency and environmental benefits, yet complex mountainous terrain and limited workspace severely restrict the transportation of large segments. To address this challenge and the limited ductility of traditional connections, this study proposes a multi-segment precast bridge column with hybrid connections (PSC-GSPT) utilizing grouted sleeves and unbonded prestressing tendons. Quasi-static tests and OpenSees simulations compared a three-segment PSC-GSPT specimen with a cast-in-place (CIP) column. Results demonstrate that the hybrid system shifts the plastic hinge above the sleeves due to their high stiffness, ensuring controlled damage. Compared to the CIP specimen, the PSC-GSPT increased peak load by 30.2% and ductility by 20.7%, while exhibiting excellent self-centering capability and 27% higher cumulative energy dissipation. Numerical parametric analysis indicates that a central tendon configuration delays yielding, boosting ductility by over 15% versus perimeter layouts, and an initial prestress level of 30% is recommended to optimize both self-centering and ductility. This study provides a theoretical basis for applying high-performance precast piers in transportation-restricted environments. Full article

Grout filling completeness (GFC) is the primary factor affecting the mechanical properties of grouted sleeve connections. To investigate the influences of vertical top void defects on semigrouted sleeve connections, two groups of samples with different rebar diameters (14/16 mm) were designed, incorporating five levels of grouting fullness gradients (GFGs): 60%, 70%, 80%, 90%, and 100%. A total of 60 semigrouted sleeve connection samples were prepared and subjected to uniaxial tensile tests and high-stress cyclic loading tests. The changes in the failure modes and mechanical responses under varying loads were systematically analyzed. The results indicated the following: (1) GFC Threshold Effect: When the GFC was less than 90%, both groups of connections failed to maintain reliable performance, with failure modes transitioning from rebar tensile fracture to interfacial bond-slip failure. Under cyclic loading, interfacial bond-slip failure occurred six times more frequently in the 16 mm-diameter samples than in the 14 mm-diameter samples, indicating significantly reduced reliability for larger diameters. (2) Uniaxial Tensile Behavior: The strength metrics of both joint groups exhibited consistent correlations with the GFC. The yield limits were weakly correlated, whereas the ultimate tensile strengths were significantly strongly correlated. The residual deformation and grout damage depth were not uniformly correlated with the GFC. As the GFC decreased, the yield phase elongation and elongation in the experimental curves generally increased. (3) High-Stress Cyclic Loading Behavior: The mechanical parameters of the 14 mm-diameter samples were not significantly correlated with the GFC. Conversely, the 16 mm-diameter samples exhibited dual dependencies on strength and deformation, with the ultimate tensile strength and grout damage depth showing strong correlations. Under cyclic loading, yield phase elongation and overall elongation decreased inversely with decreasing GFC—a trend opposite to that under uniaxial tensile loading. This phenomenon provided critical theoretical support for the ductility design of prefabricated structural joints under seismic conditions. Full article

Grouted sleeve connections (GSCs) are widely used in precast concrete (PC) bridge piers due to their convenience in construction and reliable structural performance. Corrosion-induced damage significantly compromises the seismic integrity of PC bridge piers with GSCs, making effective rehabilitation urgent. However, there is a scarcity of research addressing this specific retrofit need. To bridge this gap, this work systematically investigates the efficacy of ultra-high-performance concrete (UHPC) encasement in retrofitting the quasi-static seismic resilience of corroded GSC piers. Numerical analyses were conducted using OpenSEES, in which the GSCs were equivalently modeled by determining their yield strength and cross-sectional area. Three corrosion ratios of the GSCs (20%, 40%, and 60%) were considered. The effects of UHPC compressive strength (100 MPa, 120 MPa, 150 MPa) and different retrofit heights on the quasi-static seismic performance of the bridge piers were systematically investigated. The results reveal that corrosion of the GSCs markedly compromises the quasi-static seismic behavior of PC bridge piers, notably reducing both the bearing capacity and energy dissipation capacity. Retrofitting with UHPC shells effectively enhances the yield force, peak force, yield stiffness, and energy dissipation capacity of the piers. These improvements become more substantial with higher UHPC strength and greater retrofit height. Overall, the results underscore the significant detrimental effect of sleeve corrosion on quasi-static seismic performance and confirm UHPC retrofitting as a viable and effective mitigation approach. Full article

Grouted sleeves are commonly used to connect prefabricated structural components, but construction defects can easily occur after installation, posing potential risks to the structure. This study conducts comparative uniaxial tensile tests on 39 grouted-sleeve specimens in 13 groups—including standard specimens, defective specimens, and specimens repaired with supplementary grouting. The strain distribution patterns under different grouting lengths and loading levels are analyzed to investigate the load-transfer mechanism between reinforcement bars and grouted sleeves, as well as the influence of various supplementary grouting amounts and material strengths on the mechanical performance of defective sleeves. In the uniaxial tensile test of grouted sleeves, with grout strengths of 85 MPa and 100 MPa and HRB400-grade steel bars, when the grouted anchorage length was 4 d, insufficient anchorage length resulted in low bond strength between the grout and the steel bar, leading to bond–slip failure. When the grouted anchorage length reached 6 d, steel bar fracture occurred inside the sleeve. When the total anchorage length formed by two grouting sessions reached 8 d, specimen slippage decreased, showing a trend where the strain growth rate of the sleeve gradually decreased from the grouted end to the anchored end, while the strain growth rate of the steel bar gradually increased. The longer the total anchorage length in the sleeve after grout repair, the stronger its anti-slip capability. The bearing capacity and failure mode of the specimens depend on the strength of the steel bars connected to the grouted sleeves and the strength of the threaded connection ends at the top. Experimental results show that the anchorage length and strength of high-strength grout materials have a significant reinforcing effect on defective sleeves. The ultimate bearing capacity of specimens with anchorage length of 6 d or more is basically the same as that of steel bars. Specimens with a total anchorage length of 8 d show approximately 10~20% less slippage than those with 6 d. The safe anchorage length for HRB400-grade steel bars in sleeve-grouted connections is 8 d, even though the bearing capacity of grouted sleeves with a 6 d anchorage length already meets the requirements. Bond strength analysis confirms that the critical anchorage length is 4.49 d. When the grouted anchorage length exceeds the critical length, the failure mode of the specimen is steel bar fracture. When the grouted anchorage length is less than the critical length, the failure mode is steel bar slippage. This conclusion aligns closely with experimental results. In engineering practice, the critical anchorage length can be used to predict the failure mode of grouted sleeve specimens. Based on experimental research and theoretical analysis, it is clear that using grout repair to reinforce defective grouted sleeve joints with a safe anchorage length of 8 d is a secure and straightforward strengthening method. Full article

To improve the seismic performance of prefabricated structures, this study suggested putting grouted sleeves at the half-height of the column (at the point of contraflexure). A quasi-static test under constant axial load was conducted on the full-scale cast-in-place column and the full-scale prefabricated column connected in half-height. The hysteresis loops, skeleton curves, ductility, stiffness degradation, and energy dissipation capacity were compared. The test results indicate that the prefabricated column connected in half-height exhibited reliable seismic performance. Compared with the cast-in-place specimen, the bearing capacity of the prefabricated column decreased by only 1.45%, the energy dissipation decreased by 5.61%, and the initial secant stiffness and ductility coefficient increased by 8.88% and 9.09%, respectively. ABAQUS finite element software was used to establish finite-element models based on the experimental results. The damage pattern and seismic performance indicators of the two types of columns were verified by resolving issues related to the bonding interface model of sleeve-connected columns and the convergence of the multidimensional constitutive model. The formula for calculating the shear bearing capacity was put forward to evaluate the failure pattern. The study provides a basis for further investigation of the seismic performance of sleeve-connected columns with different connection positions under extreme conditions. Full article

As a critical element within the prefabricated structural system, the prefabricated shear wall connected by sleeve grouting is renowned for its superior mechanical performance and high construction efficiency. It is widely applied in mid- and high-rise buildings. However, under fire conditions, not only do the material properties degrade, but the structural connections may also fail, significantly compromising the structural stability and safety. Therefore, this study delves into the fire resistance performance of such prefabricated shear walls. The research primarily focuses on analyzing fire resistance characteristics, including deformation patterns, lateral and axial deformations, fire resistance limits, and other performance metrics, for both prefabricated and cast-in-place shear walls subjected to three hours of single-sided fire exposure. Additionally, a parametric analysis is performed. The results reveal that, after three hours of single-sided fire exposure, the temperature distribution patterns at the mid-width and mid-height sections of the prefabricated shear wall generally resemble those of the cast-in-place wall, displaying arch-shaped and strip-shaped distributions, respectively. However, due to the presence of sleeves, higher temperatures are observed near the sleeve areas in the prefabricated wall, along with a more extensive high-temperature zone. Throughout the three-hour fire exposure, both types of shear walls demonstrated satisfactory structural stability and thermal insulation performance, meeting the requirements for a first-level fire resistance rating (3 h). Nevertheless, greater axial and lateral deformations were noted in the prefabricated shear wall. Key factors influencing the fire resistance performance of the sleeve-connected prefabricated shear wall include the axial compression ratio, longitudinal reinforcement diameter, protective layer thickness, and height-to-thickness ratio. Specifically, axial deformation is found to be directly proportional to the axial compression ratio and height-to-thickness ratio, while inversely proportional to the longitudinal reinforcement diameter and protective layer thickness. Lateral deformation is directly proportional to the axial compression ratio and longitudinal reinforcement diameter, and exhibits a trend of initially increasing and then decreasing with an increase in protective layer thickness, and initially decreasing and then increasing with an increase in the height-to-thickness ratio. Full article

Grouted sleeve connections are widely employed in the substructures of prefabricated bridges. After installation, the grout filling condition inside the sleeves cannot be directly inspected, while grouting defects may significantly compromise the mechanical performance of the piers. This study investigates the feasibility of using the non-destructive impact-echo method to detect grouting defects in sleeves. Finite element simulation was conducted to analyze the influence of the distance between the impact point and the signal acquisition point on detection accuracy, revealing that a distance of 40–60 mm yields optimal results. Experimental findings demonstrate that the method can effectively identify grouting defects in double-row sleeves, although it cannot precisely locate the defective sleeve. A novel analytical approach is proposed, using the thickness frequency and its modes of fully grouted specimens as a benchmark. By comparing thickness frequencies at different measurement points, grout quality can be intuitively evaluated. Validation using a six-sleeve model with varying grouting densities confirmed the method’s effectiveness in detecting grouting defects in non-boundary sleeves and its practical applicability in engineering. Full article

As a key connection technology in prefabricated buildings, offshore wind power, and bridge engineering, the performance and environmental sustainability of grouted sleeve connections are essential for the long-term development of civil infrastructure. To address the environmental burden of conventional high-strength cement-based grouts, an eco-friendly sleeve grouting material incorporating industrial solid waste was developed. In this study, silica fume (15%) and fly ash (5%) were employed as supplementary cementitious materials, while nanosilica (NS) was introduced to enhance the material properties. Mechanical testing, microstructural characterization, and half-grouted sleeve uniaxial tensile tests were conducted to systematically evaluate the effect of NS content on grout performance. Results indicate that the incorporation of NS significantly accelerates the hydration of silica fume and fly ash. At an optimal dosage of 0.4%, the 28-day compressive strength reached 105.5 MPa, representing a 37.9% increase compared with the control group without NS. In sleeve tensile tests, specimens with NS exhibited reinforcement necking failure, and the load–displacement response closely aligned with the stress–strain behavior of the reinforcement. A linear relationship was observed between sleeve wall strain and reinforcement stress, confirming the cooperative load-bearing behavior between the grout and the sleeve. These findings provide theoretical guidance and technical support for developing high-strength, low-impact grouting materials suitable for sustainable engineering applications. Full article

This paper presents an investigation into the mechanical performance of a subway station prefabricated assembly air duct (PAAD), constructed by assembling the prefabricated reinforced concrete segments. The study is implemented through numerical analysis, focusing on the impact from the grouting defects in the sleeve grouting connection and assembly error defects along the assembly direction. The results demonstrate that the assembly error defect has almost no impact on the mechanical performance of the PAAD, satisfying the safety requirements for use. However, the grouting defects in the sleeve grouting connection can influence the mechanical performance of the PAAD, in which the maximum tensile stress of concrete in the sleeve grouting connection with a 20 mm-long bottom grouting defect is greater than the tensile strength of that concrete, and strengthening treatment is thus required for ensuring the structure’s safety and reliability. This study provides the basis for applying a PAAD in subway station construction. Full article

The application of precast assembled pier systems in high-seismicity regions is often constrained by their seismic performance limitations. To validate the optimization effect of GFRP confinement on the hysteretic performance of bridge piers, this study first conducted axial compression tests on 54 glass fiber-reinforced polymer (GFRP)-confined concrete cylindrical specimens. The investigation focused on the effects of fiber layers (6 and 10), orientation angles ($\pm 45°$, $\pm 60°$, $\pm 80°$), slenderness ratios (2 and 4), and compression section configurations (fully loaded vs. core concrete loading only) on confinement efficacy. The experimental results demonstrate that specimens with $\pm 60°$ fiber angles achieved an optimal balance between strength and ductility, exhibiting an average strength enhancement of 298.0% and a maximum axial strain of 2.7% compared to unconfined concrete. Subsequently, two GFRP tube-confined concrete bridge piers with varying fiber layers (PRCG1: 6 layers; PRCG2: 10 layers) and one unconfined reference pier (PRC) were designed and fabricated. All specimens employed grout-filled sleeves to connect caps and piers. Pseudo-static tests revealed that GFRP confinement effectively mitigated damage in plastic hinge zones and enhanced seismic performance. Compared to the PRC, PRCG1 and PRCG2 exhibited increases in ultimate displacement by 19.50% and 28.57%, in ductility coefficients by 18.56% and 27.84%, and in cumulative hysteretic energy dissipation by 13.90% and 26.43%, respectively. At the 5% drift ratio, their load capacities increased by 26.74% and 23.25%, stiffnesses improved by 28.91% and 25.51%, and residual displacements decreased by 20.89% and 11.17%. The accuracy and applicability of the GFRP tube-confined bridge pier model, developed based on the Lam–Teng model, were validated through numerical simulations using the OpenSees fiber element approach. Full article